The present invention relates to a device for the longitudinal stitching of multipiece printed products.
U.S. Pat. No. 4,204,626 discloses a wire-stitching device of this type in which a rotationally driven rotary stitcher is assigned to a stitching-hook closing arrangement, which is formed by a likewise rotationally driven stitching-hook closing cylinder. The axes of rotation of the stitcher and the stitching-hook closing cylinder are parallel to one another and run at right angles to the conveying direction of the products to be stitched. The rotary stitcher has a cylindrical carrier, in which a guide bush for a displaceable stitching-hook drive-in plunger is arranged, the guide bush running in the radial direction. The guide bush, which is rotatable about its radial longitudinal axis, is held in a fixed position in the radial direction in the carrier.
When the rotating stitching head meets the product advanced along an essentially rectilinear path, the U-shaped stitching hook transported by the stitching head is driven into the product in such a way that first one stitching-hook leg and then the other stitching hook leg penetrates the product and passes through the latter. During the driving-in operation, the position of the stitching-hook legs changes relative to the product. The stitching-hook legs are then bent. To this end, the stitching-hook closing cylinder has two bending elements, of which one is attached to the stitching-hook closing cylinder in a fixed position and the other is attached to the stitching-hook closing cylinder in a rotational manner. The two bending elements, as viewed in the direction of rotation of the stitching-hook closing cylinder, are arranged one behind the other in such a way that the leading bending element comes into effect on the leading leg of the stitching hook and the trailing bending element comes into effect on the trailing leg of the stitching hook.
The object of the present invention, then, is to provide a longitudinal-stitching device of the type mentioned at the beginning which enables the legs of the stitching hooks to be driven at high speed into the products simultaneously and essentially in an approximately right-angled direction relative to the products.